Examine Alex Salmond's five-year timetable for resolving Scotland's future relations with the United Kingdom and, wherever you stand on the issue of independence, it all seems remarkably straightforward. But the more you think about it, the more obvious it gets that it's not straightforward at all.

The Scottish National party version of the next five years goes like this: 2012 – consultation on the details of the question to be put to Scots about their future; 2013 – legislation by the Scottish parliament to hold an independence referendum; 2014 – campaign and referendum vote; 2015 – consequential negotiations on the transition to independence following a yes vote; and, finally, 2016 – the first general election in an independent Scotland.

Most of the political argument about this proposed process has concentrated, not unnaturally, on the early phases. Scottish politics is currently bewitched by an arm-wrestling contest between Salmond and the UK government over pre-poll issues like the date of the referendum, the question to be put to voters, and the terms of the franchise.

That arm wrestle is far from settled yet, but an outline answer may be taking shape. In the end, there will have to be a compromise over extending the vote to 16- and 17-year-olds, including a pledge to look at lowering the voting age more generally. Even more important, it looks increasingly probable that there will only be one question on the ballot paper – a yes or no on independence – but with anchoring pledges from at least Labour and the Liberal Democrats on deeper devolution in a second phase if there's a no vote on independence. In my view that's the clearest and fairest way forward.

That leaves the date. Right now that looks harder, with fewer issues of principle at stake. The SNP has briefed that its intended date is 18 October 2014. The UK government, by contrast, still sticks to the sooner-rather-than-later formula used by David Cameron in Edinburgh last month.

In the broad sweep of history, the difference between 2013 and 2014 hardly matters. In many ways the battle between the two has become a matter of political face. But if you look at the SNP timetable from the other end, from the perspective of what might happen after a yes vote in the referendum rather than before it, the difference between the two dates begins to matter rather a lot.

The impact of a yes vote in October 2014 would be tremendous. Scotland's course would have been set, and the Scottish government would begin to negotiate with London on how it would happen. Yet bear in mind three things. First, even after the vote, the decision to grant Scotland independence would still rest with the UK government and parliament. Second, the delicate political protocols of the campaign would mean that little work of substance would have been done, either in Edinburgh or London, on implementing the separation of Scotland until the vote was over. And third, politics in the rest of the UK in autumn 2014 would be focused at least as much on the forthcoming May 2015 UK general election as on Scotland.

This all raises enormous doubt about whether the negotiations and the transition to independence could possibly be carried out on the timetable that the SNP purports to expect. Unpicking the relationship between Scotland and the UK is a complex task, even assuming it is done in good faith. Agreement on the terms would not be straightforward. Assigning Scotland's share of assets and liabilities could be fraught. There would be a forest of serious issues to hack through, including the currency, the European Union and the BBC. With the best will in the world, this is tough stuff.

And then there is the 2015 general election. As soon as Scotland voted for independence, the West Lothian question would have to be confronted. It is likely there would be some immediate effort to bar Scots MPs from voting not just on English issues, but UK issues too.

But this is as nothing to the potential for instability caused by the 2015 election itself. That election would take place in Scotland too. Presumably the SNP would contest it. But the status and role of the new Scottish MPs, a majority of whom might be opposed to independence but who would all lose their seats as soon as the independence legislation was passed, would be hard to predict. Above all, there is the question of what happens if the 2015 election produces a result, as it may, which enables Labour to form a UK government that would lose its majority as soon as the Scots departed?

These are serious hypothetical questions. The prospect of highly unstable UK and Scottish politics in the wake of a yes vote is very great. It could all get uglier than we suppose. That's not, in itself, an argument against Scottish independence. But it is an argument in favour of doing what one can to minimise that possibility.

And that means, I think, holding the vote earlier, not entangling it in a turbulent UK election with a possibly close outcome. For the dignity of politics, and for the dignity of the possibility of Scottish independence, more time is needed for any possible transition. That is why it is in everyone's interests to agree that the referendum should be held in 2013, not 2014.